I believe the coax from the 91XG to the attic amp to be less than 25 feet, so I made the following change as you suggested: 91XG > downlead > LNA 100 > AC7 ch 49 input. The C2V went into the other input of the AC7. I did a rescan, then as soon as I had a chance a little while later I went back into the DVR diagnostics menu on the Roamio. Here are the results:

Channel 3-1 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 3-2 65% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 3-3 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 10-1 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 21-1 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 21-2 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 21-3 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 27-1 72% signal strength, 29 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-1 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-2 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 33-3 67% signal strength, 27 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 49-1 62% signal strength, 25 dB SNR, RS Corrected 0, RS Uncorrected 0

Channel 49-2 62% signal strength, 25 dB SNR, RS Corrected 0, RS Uncorrected

I was surprised to see improvements in signal strength and the RS Uncorrected numbers across the board. I'm not sure if the "0" for the RS Uncorrected is just temporary because I had rescanned or not. I had never seen that on any channels other than 49-1 or 49-2 when looking at in the DVR Diagnostics menu on the Tivo Roamio (I had a similar setup just the LNA 100 after the AC7 combiner but didn't see the same results). Maybe someone else can jump in with an explanation of what they think is going on or if I should leave the LNA 100 as the only amplification on my setup.

PM sent with coordinates. Thanks!

Fox SNR looking much better in latest test. Is the 91XG aimed at Fox 349 degrees magnetic?

When you removed the splitter used as a combiner, it eliminated the interference from the two sources of UHF signals created in the combiner which improved the signal strength and SNR. When you added the LNA 100 it increased the signal strength of Fox and improved the Noise Figure of the total system, which helps the SNR, as ADTech said. Only testing would tell you which preamp helps the most.

Yes 91XG aimed at 349/350 degrees.

O.K. guys I have a new question. Today, 10-1 fluctuated off the 0 RS Uncorrected to around 60 which caused some of those picture issues I described early in this thread. So, I thought I'd get in touch with Tivo to see what they could say about it.

Their reply was to be without issue, signal strength on all channels needs to be in the 80-100% range, RS Corrected and RS Uncorrected has to be 0, and SNR Levels have to be in the 30-35 dB SNR. Is there any equipment that could put me at those levels?

There are two possible reasons for the increase in uncorrected errors for 10:

1. Local electrical noise interference on VHF-hi, which has higher noise levels than UHF. If the noise is constant, then you should also see a reduced SNR. I have a fairly strong CH 10 signal, but its SNR is only 16 because I also have a high noise level on VHF-hi.

2. Multipath interference for the CH 10 signal. This could be from static reflections, or it could be dynamic multipath from moving objects, like vehicles or aircraft, or when signals have to filter thru trees that are moving in the wind. A possible solution would be to use a more directional VHF-hi antenna to replace the V in the C2V. I think the C2V has an integrated UVSJ, so you might need an external UVSJ to combine the new VHF-hi antenna with the C2V.

IF the problem is multipath, and IF a more directional VHF-hi antenna helps, then another alternative would be to replace the C2V with a UHF/VHF-hi combo antenna.

Check out this theory with ADTech before doing anything drastic.

IIRC, the early TiVo tuners didn't handle multipath reflections very well.
https://www.google.com/?gws_rd=ssl#q=TiVo+tuner+doesn't+handle+multipath+very+well

You could test this theory in a low-cost way by connecting your antenna system (or just the C2V) directly to a TV and see if there was any difference.

OTA signals are constantly changing. If you want a real-time side-by-side comparison between two tuners, you can insert a splitter after the antenna system to feed the Roamio tuner and a TV, and feed a second TV connected directly to the splitter.

If something bad happens as shown on the TV connected to the Roamio tuner, you can see if it also happens to the TV connected directly to the splitter.

I forgot; where are your antennas located, inside or outside?

Those reading would be ideal, but your own tests have shown that for satisfactory reception the signal strength can be lower, and the SNR can be as low as 18 dB (15.5 dB at 0 NM is minimum). I do agree with them about the errors.

http://forum.tvfool.com/attachment.p...1&d=1415035118

Maybe, but it would be more expensive than necessary.

Thank you for addressing this! I told them I felt like it would be quite difficult for all OTA users to get to those levels to which they replied that they were sure there was equipment that would do it.

What I wasn't sure about is whether an increased SNR strength number correlated to no error messages (RS Uncorrected and RS Corrected numbers). That's a big reason why I wanted to know if those numbers they suggest are realistic.

While Tivo has the most superior OTA DVR, I feel their customer support for OTA users is lacking.

Yeah I want to hear from ADTech as well to see his thoughts. My antennas are roof mounted. There is no doubt inserting the Winegard LNA 100 to the 91XG line before that signal goes into the AC7 combiner improved things. I didn't expect it to raise the signal levels for all channels too....

I thought I remember reading that the Roamio had a pretty good tuner and was an improvement over the Premiere.....

I should also add I have noticed a small error number appear on 33-1 as well since implementing the changes ADTech suggested. But, it hasn't been as consistent as the 10-1 error number.

Me too; he is pretty sharp and knows what he is talking about. I have learned a lot from reading his posts not only on this forum but other forums as well.

In one of your earlier threads StephanieS told you to get a HAM (someone who as an FCC license to operate radio amateur transmitting equipment) to help you. I'm not there to help you, but I have been a ham for over sixty years. I'm now 81 and have been doing antenna experiments since I was 8 when I built my first crystal set and used my bedspring for an antenna. I would fall asleep with my headphones on listening to WOR AM 710 in NJ.

correct

Their readings are based on standards for cable systems for digital signals (QAM). The 8VSB OTA signal contains a pilot signal that helps with marginal reception; the QAM signal does not contain a pilot signal.

33.1 KSPR real channel 19 is your strongest signal. It could be getting close to an overload point somewhere in your system.
http://www.tvfool.com/?option=com_wr...d24362e8886d03

Try the two tuner side-by-side comparison I suggested to see if it happens on both tuners.

A few observations about the most recent discussions.

Tivo's statement of the required SNR, as rabbit73 already noted, is bogus. They were quoting QAM information, not ATSC. A perfectly tuned ATSC transmission plant rarely does better than 35 dB or so. However, since the Roamio does have four tuners, it would be safe to assume that they have integrated an input amplifier followed by a four port splitter into the front end of the tuner so as to best avoid splitter loss while doing their best to maintain a low input noise figure and a reasonable input signal power capacity.

I'm not. That's why I suggested the configurations previously, to get rid of system configuration errors that were degrading the SNR.

Nope. Tuners are equipped to handle a lot more than your system can possible feed to it.

Upon receiving your coordinates, they resolve to the northeast corner of your roof where aerial photos show a satellite dish installed. I've surmised that you're using that existing mount for the 91XG.

Based on your coordinates, you're about 200' below the rim of a steep hillside across the creek valley. The signal path to KRBK crosses the highest elevation near the intersection of N 3rd and E. Indian Valley Dr. then drops towards you, then finally into the valley. It has been my experience and observation that the closer one is to the terrain obstacle causing the diffraction of the signal, the more inaccurate is the guesstimate of received signal strength from the TVFool simulation engine. I suspect that the signal forecasts for KRBK's signal is probably too optimistic.

In all, the one change I'd recommend making will be exceptionally difficult and that's getting the 91XG up to the peak of the roof of the second story instead of down low on the old satellite mount at the back of the garage. That would likely get you an additional 20+' of elevation and I'd expect it to help tremendously with your reception of KRBK. I'd also expect a serious level of difficulty getting it up there.

It is VHF being received by a simple not-very-directional dipole. Most likely due to impulse or electrical noise from nearby.

I think he's fine as long as he doesn't amplify the C2V's output. If we accept the simulator's estimate of about -25 dBm at the antenna, add in 8 dB for antenna gain, subtract 1-2 dB for the insertion loss of both the AC7 and integrated U/V combiner, subtract 3 dB of coax loss (about 50'), and subtract the Roamio's tuner noise figure (??), we're still well under -20 dBm signal power at the inputs to the individual tuners which would be expected to tolerate maximum signals up to nearly 0 dBm.

Is this the comparison you are suggesting (see bold):

OTA signals are constantly changing. If you want a real-time side-by-side comparison between two tuners, you can insert a splitter after the antenna system to feed the Roamio tuner and a TV, and feed a second TV connected directly to the splitter.

If something bad happens as shown on the TV connected to the Roamio tuner, you can see if it also happens to the TV connected directly to the splitter.

Is there any risk damaging a TV tuner sending that much signal to a single tuner? So you are taking about inserting a two out splitter after the output of my AC7 combiner (one output to the Roamio and one output to a 2nd televison)? If so, I can try but it may be tough to catch since I don't have 2 TV's in the same room.

Before I answer your last question, I need to be sure that I understand your present new setup that is working the best so far. Is there anything between the AC7 and the input of the Roamio other than the coax?

AC7 > coax ? ft > input of Roamio > TV

or in greater detail:

Are you trying to power the preamp thru the AC7, or doing it locally at the preamp location with its AC adapter?

Yes, I am using existing satellite mounts for both antennas. I'm not sure my spouse would go for putting the 91XG up on the very highest point of the roof (at the 2nd story). But, let's say she did what would I need to put it up there? Since the changes you suggested the SNR fluctuates back and forth between 24 and 25 dB on the SNR level (60-62% signal strength).

For what its worth when I checked 10-1 and 33-1 today in the DVR Diagnostics menu both of the RS Uncorrected Levels were back at 0 (along with all other channels being at 0). It sounds like you are saying the fluctuations on those channels may be something that is beyond my ability to control or fix. Is that fair to say? Not sure if it's possible at this point or not since the house is finished but would quad shield RG6 possibly fix it?

Your drawing appears to show the current configuration. The coax from the 91XG connects to the Winegard LNA 100 and from there into the single channel input of the AC7 combiner. The C2V coax connects directly to the other input of the AC7. The output to the Roamio TV is being connected with these F barrel connectors:http://www.amazon.com/10pcs-Frequenc...=vglnkc3181-20

I also use the F81 connectors when a cable is too short. The ones you show look to be excellent quality. The cheap ones don't grab the center conductor of the coax very well. You can test an F81 by inserting a piece of 18 gauge solid copper wire, which is the same gauge as the center conductor of RG6.

Your 91XG is doing OK for Fox. I'm more concerned about what is causing the errors for 10.1 and 33.1 which would make a DVR recording less than enjoyable.

Are you trying to power the preamp thru the AC7, or doing it locally at the preamp location with its AC adapter?

I need to think a little more about my answers, and will come back later.

I agree about the DVR recordings! It might be a lot of trouble but do you think rewiring with RG6 Quad shield coax would "fix" it or is this something simpler?

I would like to answer your question about the preamp but I am afraid I unfortunately don't understand what you are asking.

The LNA100 isn't a "pre-amp", it's a "back of the set" type of amp without the capability of using a remotely located power inserter. It has to be powered locally (to the amp) from a wall-wart. I suggested it because it has a very low noise figure and a very good tolerance to strong signals, both characteristics that I've verified. Besides, it was already on hand!

As for the intermittent errors on 10.1 and 33.1 from Fordland, I don't know. Might have been from something as mundane as a burst of noise from a switched device, might have been some wind-induced multipath that the decoder couldn't correct.

It's understandable about not wanting to move the 91XG up to the second floor peak should that be needed, it looks like it would be a very big job.

Swapping the C2V to a more directional 7-51 antenna would likely improve those SNRs, but the replacement antenna would be far larger. TANSTAAFL, you know.

Quad Shield won't make a difference.

Thanks for the correction.

I had remembered that he ordered the AC7 with power pass-thru and was concerned about the location of the splitter. As you correctly pointed out, the LNA 100 has an AC adapter, but it doesn't have a power inserter, so it can't be powered thru the AC7.

Yes
Not that I can tell, but there is no way I can guarantee that nothing bad will happen if you try it. If you dropped your TV while moving it, you would curse me. I believe in non-destructive testing, not testing to destruction.

I always learn something from every one of my antenna tests.

You are already sending that much signal to your Roamio in your present setup. What I'm suggesting would send half as much to it:


What I'm looking for are some clues for further improvement.

You are now on your 5th thread for your reception problem. You have made a lot of progress, and have learned a lot, but have reached the point of diminishing returns as ADTech has implied. At the beginning, you got a large improvement with little effort; now a large effort is needed to get even a small improvement.

Only you can decide if the possible benefit of the test is worth the trouble and risk. I am curious about what is causing the errors, but not curious enough to force you to do something against your will.

If you do make the side-by-side comparison test, the results might be inconclusive.

If you want to quit at this point, and settle for the improvement you already have, that's fine with me.

There is another type of interference that might be causing you problems, which is from strong local signals from other services like paging transmitters, police, fire, and taxi.